Thorax:Arterial structure:Coronary arteries
There are two coronary arteries are arising from the aortic sinuses at the beginning of the ascending aorta. Left main coronary * Arises from left coronary sinus * Courses behind right ventricular outflow tract, between pulmonary trunk and left atrium. * Branches: bifurcates into LAD and LCX * Commonly trifurcates into LAD, LCX, and ramus intermedius ** RI may follow the course of obtuse marginal or diagonal branch Left anterior descending * Continuation of LM and runs along anterior interventricular groove and distally, wraps around apex and and form collaterals to distal PDA * Occasionally dives into left ventricular myocardium, forming "myocardial bridge" * Diagonal branches run diagonally over anterior left ventricular wall ** Numbered sequentially from proximal to distal (D1, D2, D3) ** Supply anterolateral wall * Superior septal perforator branches extend into interventricular septum and anchor LAD to myocardium ** Septal perforators supply anterior 2/3 of septum ** 1st septal perforator commonly supplies His bundle and branches of AVN * Right ventricular branches are small but may form collaterals to RCA * Segmentation ** Proximal LAD: End of LM to 1st large septal or D1 (1st diagonal), whichever is more proximal ** Mid LAD: End of proximal LAD to 1/2 the distance to the apex ** Distal LAD: End of mid LAD to end of LAD Left circumflex artery * Arises from LM at nearly perpendicular angle and runs around mitral annulus in left atrioventricular groove and anastomosing variably at the end with the right coronary artery. * Gives off obtuse marginal branches (OM1, OM2, OM3) that runs down the left border of the heart. * Distally, the LCX becomes diminutive unless left dominant, where it branches into posterior left ventricular and posterior descending artery * Supply: lateral free wall and portion of anterolateral papillary muscle * Segmentation ** Proximal LCX: End of LM to origin of OM1 (1st obtuse marginal branch) ** Mid and distal LCX: Distal to OM1 to end of LCX or PDA origin Right coronary artery (RCA) * Arises from right coronary sinus * Passes under right atrial appendage and descends into right anterior atrioventricular groove to the inferior border of the heart. * In 50%, 1st branch of RCA is conus branch ** passes upwards and medially on the front of the conus ** supplies right ventricular outflow tract * In 60%, SAN is the next branch ** 40% take alternative supply from LCX atrial branches ** passes back between right auricle and the aorta * Gives off right marginal artery that passes to the left along the right ventricle inferior border. * If right-dominant circulation, RCA bifurcates into PDA and PLV at the diaphragmatic surface of the heart * PDA runs along posterior interventricular groove and supplies posterior 1/3 of inferior septum * PLV courses cephalad and is usual source of AVN branch. * Segmentation ** Proximal RCA: Ostium to 1/2 the distance to acute margin of heart ** Mid RCA: End of proximal RCA to acute margin ** Distal RCA: Acute margin to PDA origin Dominance and variations * Dominance is defined by supply of PDA and PLV * There are right-, left-, and codominant coronary systems * ~ 85% are right dominant (RCA supplies PDA and PLV) * 8% are left dominant (LCX supplies PDA and PLV) * 7% are codominant (RCA and LCX share supply of PDA &/or PLV) * Rare super-dominant RCA supplies territory of diminutive LCX (circumflex from RCA) * Rare wrap-around LAD supplies PDA * Ramus intermedius in 10% i.e. trifurcation of the LCA. * Absence of RCA or LCA * RCA from pulmonary trunk * Intramural coronary artery, most commonly LAD.